Heating structure



Dec. 5, 1967 L M WATSON 3,356,835

HEATING STRUCTURE Filed Oct. 8, 1964 2 Sheets-Sheet 1 l u h u uINVENTQR.

Y LEE M. WATSON FIG. I zmzz z ATTQRNEY Dec- 1967 M. WATSON 3,356,835

I HEATING STRUCTURE Fiied Oct. 3, 1964 3 v 2 Sheets-Sheet 2 FIG.4 F G gINVENTOR. LEE M. WATSON ATTORNEY United States Patent G 3,356,835HEATING STRUCTURE Lee M. Watson, South Bend, Ind., assiguor to TheSinger Company, New York, N.Y., a corporation of New Jersey Filed Oct.8, 1964, Ser. No. 402,481 5 Claims. (Cl. 219-549) The present inventionrelates to a heating structure and more particularly to a specialheating wire construction for use in various heatingstructures.

In the melting of snow and ice from pavement, walks, steps, runways andthe like, the use of electrical heating wire has, in recent years, beenemployed extensively by embedding the wire in the pavement and otherstructures. This wire is embedded beneath an inch or two of pavingmaterial and is used to maintain the surface of the pavement above thefreezing point. While the individual, singlestrand heating wire laidback-and-forth in the pavement has been used to a limited extent, thistype of heating installation is difficult and time consuming to make andmay result in a heterogeneous pavement structure. In recent years, aheating structure has been made available, which consists of an opentype metal wire mesh an which is mounted in a predetermined pattern, aninsulated heating wire secured in place by means spaced along the wire.Since there is always a possibility that the insulation on the heatingwire or the entire insulated heating wire will be broken, in theinterest of safety, the metal wire of the mesh is grounded so thatshould the mesh become charged, the current will not be conductedthrough the wet concrete or standing water to a person standing on thepavement. The grounded wire mesh constitutes an ef-' fective means ofgrounding the embedded heating wire unit so long as the mesh is in goodcondition; however, the metal mesh occasionally will eventuallydisintegrate from rust and lose its ability to ground the heating wire.Further, in order to reduce the cost of the initial installation,a'plastic mesh has been used in place of the metal mesh and,consequently, this unit has not, in the past, been effectively grounded,and therefore, under certain conditions, is dangerous to personsstanding or walking on the pavement. It is therefore one of theprincipal objects of the present invention to provide a heatingstructure of the foregoing type which is, at all times, effectively andreliably grounded, regardless of the type or condition of the mesh andwhich will remain effectively grounded under all operating conditionsfor the life of the pavement in which the heating structure is embedded.

Another object of the invention is to provide a heating unit of theforegoing type, in which the heating wire is effectively shielded fromdamage, abrasion, nicks and cuts to which it may be subjected duringfabrication, installation and operation of the heating unit, and whichcan readily and easily be secured to the mesh, particularly to varioustypes of plastic or other non-metallic mesh struc tures.

Stillanot-her object of the invention is to provide a heating wire whichwill give maximum safety and protection to any structure in which it isincorporated and to persons coming into contact therewith, and which hassubstantially longer life in service than conventional heating wire forcomparable uses.

A further object is to provide a rugged, versatile heating wirestructure which can be bent or flexed into various configurations withnumerus and intricate curved portions and which is highly flexible andadapted to conform readily and fully to the contoured surface in whichit is mounted orsec'ured. I

' Another object of the invention is to provide a heating wire structurehaving a ground conductor which becomes effective whenever the externalinsulation of the wire is "ice broken and which can be groundedeffectively at any number of places along the wire and at either endthereof.

Additional objects and advantages of the invention will become apparentfrom the following description and accompanying drawings, wherein:

FIGURE 1 is an enlarged plan view of a heating structure having thepresent wire structure incorporated there- FIGURE 2 is a vertical crosssectional view of the heating structure shown in FIGURE 1, the sectionbeing taken on line 2-2 of FIGURE 1;

FIGURE 3 is an enlarged fragmentary view of the heating wire shown inthe preceding figures with portions of the heating wire broken away tomore effectively illustrate the construction thereof;

FIGURE 4 is a transverse cross sectional view of the heating wire shownin the preceding figures, the section being taken on line 44 of FIGURE3;

FIGURE 5 is an enlarged view of another portion of the heating structureshown in FIGURES 1 and 2, illustrating the manner in which the heatingstructure and heating wire are grounded; and

FIGURES 6, 7 and 8 are schematic diagrams of practical predeterminedarrangements of the heating wire on the mesh, which can be effectivelyused in pavements, walks, driveways and the like for melting snow andice.

Referring more specifically to the drawings, and to FIG- URES 1 and 2 inparticular, in which one embodiment of the present invention isillustrated, numeral 10 designates a flexible mesh which may be of anysuitable material; however, in the interests of economy including easein fabrication, it is preferably constructed of plastic or fiberglassmaterial, the mesh being illustrated as having longitudinal andtransverse strands 12 and 14, respectively, joined together byheat-sealing at the points of intersection, indicated by numeral 16, orby any other suitable joining means. The particular open type meshconfiguration is not important and various types of structures otherthan separate strand or wire construction may be used. For example, themesh may be of the expanded plastic or metal type of a perforated sheetof plastic or fiberglass material. The mesh should be of the open typeconstruction so that when the heating structure is embedded in theconcrete, the concrete will flow readily through the spaces between thestrands and form a homogeneous and monolithic structure. The mesh,whether plastic or metal, will, in most installations, give some degreeof reinforce-. ment to the concrete or pavement structure and serveeffectively as a carrier for the heating wire so that the heating wirecan be transported and laid in a mini-mum amount of time and with asmall amount of effort.

The heating wire 20 is mounted on the flexible meshand is secured,attached or held thereon or adjacent thereto by any suitable means, suchas, either by a physical or chemical bond or by loosely or tightlyconnected securing means. While it is preferable to hold the heatingwire 20 in a fixed position on mesh 10 so that the longitudinalheatingsections and curved sections will not become displaced and form hot andcold spots in the structure, it is not necessary that the heating wirebe joined rigidly or firmly in a particular place and may be permittedto slip laterally, within a limited range, and

sulation for the heating wire. The ground wire 34 may be of other thanbraided construction. For example, it may consist of a Wire helicallywound around layer 32 or it may be a layer of foil or the like. Layer 32may be of any suitable flexible insulating material, such as plastic,rubber or fiber, and the outer layer is preferably thermoplasticmaterial, although other suitable insulating materials may be used.Layer 34'i's constructed of relatively fine metal Wire, preferablycopper, and the completed layer should be highly flexible so that itwill not interfere with the overall flexibility of the final wire.

In fabricating'thewire structure, the inner insulating material 32 isfirst extruded on wire 30, and after it has fully set, the Wire 34 isbraided tightly onto the external surface of insulation 32; Thereafter,the outer insulation 36, of thermoplastic material, is extruded onto thebraided structure, forming an effective connection therewith. Theheating wire fabricated in'the foregoing manner is mounted on the opentype mesh, illustrated in FIGURES 1, 2

and 5, by. pressing the heating wire firmly against the strands of themesh, and preferably while the pressure is applied thereto, heating thestructure to a temperature where the thermoplastic outer insulationmaterial 36 will eitherfuse with the plastic strand material or willform a physical bond therewith by embracing the strands in contacttherewith. In order to form the optimum bond or joint between theheating wire and the'strands of the mesh, a relatively thick outerinsulation layer 36 is provided, so that the strands'may be, in effect,embedded in the insulation material wherever the strands cross theheating wire. In this type of structure the heating wire is held firmlyin place on the mesh and Will not slide or sliprelative to the meshstrands; Other methods of securing the heatingwi-re to the mesh maybe'used, including clips extendingover the wire and preferably spacedalong:

the Wire throughout substantial portions o'fits'length. If desired, thewire may be laced or otherwise woven into the mesh so that it crossesover and under the strands on which it lies transversely. Further, itmay be held by a second mesh secured to the first mesh. The second meshforming spaced securing meansalb'ng the wire and being of an open typepermits the first mesh to functionin the normal manner in'the'installation. The'braidedwire layer 34 is intended, primarily, toserve as a ground for the heating wire so that if the inner insulation32 is broken at anyplace alongj'the' heating wire, the current will beeffectively grounded. One method of grounding the structure isillustrated in FIGURE 5, wherein a' short length of braided wire shield34' is removed from inner insulation 32 and connected to a ground wire40 byconnector 42, the ground wire 40 being connected to 'an effectivegrounding device, such as a water pipe or a rod extending deeply intothe earth.-

After the heating structure has been fabricated in the foregoing manner,i.e. with the heating wire secured or connected to or otherwise mountedon the mesh at the fabrication plant, the mesh is usually'rolled, foldedor otherwise placed in a compact condition and shipped to the place ofinstallation. A first layer of concrete or paving material is poured andthe heating structure is placed on top of the initial layer and a secondlayer of concrete or other pavement is immediately poured on top of thefirst layer and the heating structure. Since the first layer has not hadadequate time to set, the second layer forms an integral structuretherewith, thus resulting in a monolithic structure in the entirepavement.

During the installation or use of the heating structure, if theinsulation 32 should be broken or ruptured, the metal wire 34' willeffectively conduct the current to the ground wire 40, regardless of theposition in the wire in which the break occurs. While the braided wirelayer 34 is of a corrosion resistant material, it is also protected forlong life by the outer insulating layer 36 and is protected thereby fromcorrosion, abrasion, nicks and cuts.

Although the present invention has been directed primarily to theheating wire with the braided ground structure mounted on a flexiblemesh, the heating wire structure may be used for other purposes apartfrom the mesh. Only one embodiment of the present invention has beendescribed in detail herein; however, various changes and modificationsmay be made without departing from the scope of the invention.

I claim:

1. A heating structure for embedding in pavement and the like, where thestructure encounters water and moisture and which is subjected to abuseand strain during installation and use, saidstructur'e comprising a meshof fiberglass material of open type construction having longitudinallyand transversely arranged strands between which the paving material willreadily pass, an electrical heating wire secured to said mesh in asinuous path, said heating wire having an electric resistance wire, aninner insulating layer of plastic material on saidwire, a braided wireforming a protective shield and an electric ground layer around saidinner insulating layer extending substantially the full length thereof,and an outer insulating 2. A heating structure for embedding in pavementand the like, where the structure encounters water and moisture andwhich is subjected to abuse and strain during installation and use,saidstructure comprising a mesh of fiberglass material of open typeconstruction having spaced strand-like members between which the pavingmaterial will readily pass, an electrical heating wire held adjacent tosaid mesh in a sinuous path, saidheating wire.

having an electric resistance wire, an inner insulating layer of plasticmaterial on said wire, a braided wire forming a protective shield and anelectric ground layer around said inner insulatinglayer extendingsubstantially the full length thereof, and an outer insulating layer ofthermoplastic material around said braided wire, said outer layer beingrelatively thick and engaging members of said mesh and securing, saidheating wire to the mesh.

3. A heating structure for embedding in pavement and the like, where thestructure encounters water and moisture andwhich is subjected to abuseand strain duringinstallation and use, said structure comprising a meshhaving; spaced members through which the pavingmaterial will readilypass, an electrical heating Wire connected to said mesh in a sinuouspath, said heating. wire having an electric resistance wire, an innerinsualtinglayer of plastic material on said wire, a braided wire forminga protective shield and an electric ground-layer around said innerinsulating layer, an outer insulating layer around said braided wire,said outer layer being relatively thick and embracing members of saidmesh for securing saidheating wire to said mesh carrier.

4. A heating structure for embedding in pavement and the like," wherethe structure encounters water and moisture and which is subjected toabuse and strain during installation and use, said structure comprisinga flexible carrier of perforated plastic material construction throughwhich the paving. material will readily pass, an electrical heating Wiremounted on said carrier in a sinuous path, said heating wire having anelectric resistance wire, an inner insulating layer of plastic materialon said wire, a braided wire and a protective shield forming an electricground layer around said inner insulating layer extendingi substantiallythe full length thereof, and an outer insulating layer of thermoplasticmaterial around said braided wire, said outer layer being relativelythick and engaging said carrier and securing said heating wire' to themesh.

5. A heating structure for embedding inpavement and the like, Where thestructure encounters water and moisture and which is subjected to abuseand strain during installation and use, said structure comprising aflexible carrier, of perforated construction through which the pavingmaterial will readily pass, and electrical heating Wire mounted on saidcarrier in a sinuous path, said heating Wire having an electricresistance wire, an inner insulating layer of plastic material on saidWire, a layer of electrical conducting material forming a ground aroundsaid inner insulating layer extending substantially the full lengththereof, and an outer insulating layer disposed around said lay-er ofelectrical conducting material and securing said heating wire to themesh.

References Cited Watter 219377 Warner 174107 Dion 219-529 Cox 219528Berry 219--549 Chapman 219-528 Watson 219549 FOREIGN PATENTS 12/1924Great Britain. 942,142 11/ 1963 Great Britain.

RICHARD M. WOOD, Primary Examiner.

VOLODYMYR Y. MAYEWSKY, Examiner.

1. A HEATING STRUCTURE FOR EMBEDDING IN PAVEMENT AND THE LIKE, WHERE THESTRUCTURE ENCOUNTERS WATER AND MOISTURE AND WHICH IS SUBJECTED TO ABUSEAND STRAIN DURING INSTALLATION AND USE, SAID STRUCTURE COMPRISING A MESHOF FIBERGLASS MATERIAL OF OPEN TYPE CONSTRUCTION HAVING LONGITUDINALLYAND TRANSVERSELY ARRANGED STRANDS BETWEEN WHICH THE PAVING MATERIAL WILLREADILY PASS, AN ELECTRICAL HEATING WIRE SECURED TO SUCH MESH IN ASINUOUS PATH, SAID HEATING WIRE HAVING AN ELECTRICAL RESISTANCE WIRE, ANINNER INSULATING LAYER OF PLASTIC MATERIAL ON SAID WIRE, A BRAIDED WIREFORMING A PROTECTIVE SHIELD AND AN ELECTRIC GROUND LAYER AROUND SAIDINNER INSULATING LAYER EXTENDING SUBSTANTIALLY THE FULL LENGTH THEREOF,AND AN OUTER INSULATING LAYER OF THERMOPLASTIC MATERIAL AROUND SAIDBRAIDED WIRE, SAID OUTER LAYER BEING RELATIVELY THICK AND EMBRACING THESTRANDS ENGAGED THEREBY AND FORMING BOND THEREWITH SECURING SAID HEATINGWIRE TO SAID MESH CARRIER.